datas only written in main column (wunderbaum-0.14.1)

[chromvit]

I am new at wunderbaum. After reading Quick Start, I tried a simple tree but the datas are not written to col1 or col2.
I tried two "source" definitions with the same result. What have I overlooked in the manual?
tree1.html

[chromvit]

As written in the Grid chapter rendering: "Wunderbaum renders the first column (the main node column) by default. To render additional columns, implement the render(e) callback." After adding a rendering it works.